Question

How do answer an equation that have decimals/ percentage

Answer 1

Do the same thing like 
0.2x+0.2=4
0.2x=4-0.2
0.2x=3.8
x=3.8/.2
x=19

For percent, 
What is 8% of 54
8%=0.08
0.08 * 54
4.32 is the answer

Like that. I hope this is what you are looking for. I'm sorry if it isn't

Answer 2

If you had an equation such as 50%x=20, I would convert the percent to a decimal first. So, 0.50x=20. Then I would change the decimal into a simplified fraction. In this case it is 1/2. So, 1/2x=20. Then I would reciprocate the fraction and multiply that by 20. So x=20*2/1. From this, we would get x=40/1, but the 1 is not necessary, so we can write the final answer as x=40.